Cream the butter until light and fluffy, then gradually add the sugar. Continuing to beat, add the eggs one at a time, beating well, on medium speed, after each addition. Gradually add the orange juice and rind. Meanwhile, sift the flour with the baking powder and salt and gradually add to the batter. Add the walnuts last, blend another minute on medium high speed, and pour into a greased and lightly floured 8-inch tube pan. Bake in a moderate oven (350 F) for 25 to 30 minutes until the color is a light chestnut and the cake springs back to the touch. (Watch carefully because this cake bakes quickly.) Turn onto a wire rack, round side up. Dust with confectioners’ sugar and cool thoroughly before slicing.